Conventionally, light emitting elements using nitride semiconductor are widely used for blue light emitting diodes and the like. Recently, ultraviolet light emitting diodes (LED) having an emission wavelength in a shorter wavelength region, for example, at a 370 nm band region are under development.
However, when an ultraviolet light emitting device having an emission wavelength of less than or equal to 375 nm is produced, emission of the yellow visible light band (so called “deep emission”) is observed, and the phenomenon that the emission color of the device turns strongly whitish arises. This phenomenon leads yellow or white light emission although the light of the ultraviolet region is intended to be radiated, and leads the problem that the monochromaticity of the radiated light cannot be achieved due to the noise by the visible light component by the deep emission. Also, there is a problem that radiation of the light having a wavelength other than the required wavelength causes deterioration in the light emitting efficiency itself. The deep emission appears significantly in a light emitting device that emits short wavelength light of the ultraviolet region or the like.
While it has been thought that the deep emission is caused by emission in a defect or in an impurity level in the light emitting layer, this thought is still unclear.
In Non-patent Document 1, some influence by C (carbon) on the deep emission is discussed based on the measurement of photoluminescence.